1. Field of the Invention
The present invention relates to a business telephone system connected to a plurality of telephone lines with caller ID logging for logging caller ID information records on a per telephone line basis.
2. Description of the Related Art
Business telephone systems are telephone systems that have a plurality of telephone stations (i.e. telephone sets or telephones) connected to a central system control unit or processor. The central processor is connected in turn to one or more telephone lines or trunks. The telephone lines connect the central processor to a Central Office (CO) of the telephone company to which the owner of the business telephone system subscribes; the plurality of telephone stations thus share the one or more telephone lines. The processor handles switching of the incoming calls between the telephone stations, intraconnecting of system telephones for conference calls, storing of voice mail messages for the individual stations, and other functions. The COs now optionally provide on the telephone line the number of an incoming call, a name associated with that number, and other information in a service denoted incoming caller line ID (ICLID). Subscribers to the service may have the ICLID information displayed when the incoming call causes one of the telephone stations to ring. A further function that is particularly advantageous for small businesses is an ICLID record logging function in which the ICLID information is stored as a record in a memory, and is then available for subsequent recall.
Prior art business telephone systems that have ICLID logging include a separate memory device or space arranged for each telephone station to store ICLID records. The memory space of these prior art devices is divided into respective sections on a per station basis and each station can access only its section of the memory. Each section stores a predetermined maximum number of records. In these prior art devices, each ICLID record must be saved in multiple sections of memory if more than one of the telephone stations is to have access to the information. Once a section of memory is full and another record is required to be stored, the oldest record in that section must be discarded to store the new record. This creates an inefficient use of memory, forcing system designers to choose between an expensive device in which each memory section is large enough to store an acceptable number of ICLID records and a less costly device that unsatisfactorily limits the number of ICLID records that can be stored.